The present invention relates to a dynamoelectric machine, such as a salient pole generator-motor, including a ventilating and cooling device.
A generator-motor installed in a conventional pumping-up hydroelectric power generating plant is rotated in different directions when operating as a generator and when pumping up water, so that there is generally adopted a ventilating system in which cooling air is circulated, regardless of the direction of rotation, by a motor driven fan used for forced ventilation and cooling.
This type of ventilating and cooling device will be described with reference to FIG. 1, wherein there are provided a hub 2 mounted on the outer periphery of a shaft 1, a yoke 3 connected to an end of the hub 2 through a cotter key (not shown), and a plurality of poles 4 connected to the outer peripheral face of the yoke 3 by dovetails or the like (not shown). These elements 1 through 4 constitute a rotor. On the other hand, a stator core 5 with winding 7 mounted thereon is supported by a stator frame 8. Air which is warmed up during passing through the machine is cooled by an air cooler 9 attached to the stator frame 8. At the axial ends of the stator frame 8, there are provided motor driven fans 10 for forcing the cooled air into the machine. Reference numeral 11 represents a foundation made of concrete or the like.
The flow of the cooling air during the operation of the generator-motor is as shown by arrows. That is, the cooling air from the air cooler 9 is drawn by the motor fans 10 and flows upward or downward. The cooling air is boosted by the fan 10 and then flows into the machine in which the air flows through spaces between adjacent poles in the axial direction and into ventilation ducts 6 in the stator core 5. The air then flows through openings 8a provided in the stator frame 8 into the air cooler 9.
The cooling air which is forced into the machine by the motor fans 10 is required to enter the spaces between the adjacent poles which rotate at a high speed, so that the cooling air collides with the ends of the poles at the entrance of the spaces between the poles, which generates a loss in the air flow.
Now, some analysis of the phenomenon of collision of the cooling air with the ends of the poles is made with reference to FIGS. 2A and 2B. In FIG. 2B, U denotes the peripheral velocity of the rotor. In the vector diagram of FIG. 2A, various velocities relative to the peripheral velocity of the rotor are shown. As will be appreciated, the cooling air flows in a direction of the vector sum V1 of the peripheral relative velocity Vt which is substantially the same, in magnitude, as the peripheral velocity U of the rotor and the axial flow speed Va1 at a speed of V1, so that the cooling air collides with the poles at the speed of V1. As a result, the windage loss due to the collision of the cooling air with the poles at the entrance of the spaces is increased, so that in the generator-motor for use in a large capacity pumping-up power plant, one had to choose either to use a costly large output motor fan which is capable of generating an extremely high pressure with the associated disadvantage of an extensive increase in windage loss or to adopt other ventilation systems of complicated construction wherein, for example, ventilation is made separately for the stator and the rotor in order to obtain a desired amount of the cooling air. Thus, the prior art ventilation system is associated with a great amount of energy waste or is costly.